a) Field of the Invention
The present invention is broadly concerned with concrete blocks, pavers and tiles adapted for use to complete the construction, decoration and/or "landscaping" of a patio, a garden or any other area subjected to pedestrian traffic.
The invention is more particularly concerned with a block of the above-mentioned type, which is made from a polymer concrete mix containing stabilized wood aggregates and thus is lightweight, and which also has an enhanced mechanical resistance making it particularly efficient for its intended use.
By the expression "a lightweight block" as is used in the present specification, there is meant a block having a density of about 800 to about 1,200 kg/m.sup.3, i.e., a block having a bulk density equal to 1.+-.0.2.
b) Brief Description of the Prior Art
Stabilized wood aggregates and their incorporation as additives into a concrete or a mortar for the manufacture insulating construction elements, such as prefabricated walls or floors, are already known. In this connection, reference can be made to Canadian patent No. 1,171,264 granted on Jul. 24, 1984 and to Canadian patent No. 1,203,991 granted on May 6, 1986, both in the name of Societe Francaise d'Agregats Stabilises.
The first one of these two Canadian patents discloses and claims a process for the manufacture of stabilized wood aggregates, which comprises two basic steps, namely (1) a sterilization of wood chips by thermal treatment in a rotary kiln at a temperature ranging from 400.degree. to 800.degree. C., and (2) a subsequent chemical treatment of the sterilized wood chips to convert them into the required aggregates. This chemical treatment is carried out first by spraying onto the sterilized wood chips a solution of a calcium salt, preferably calcium chloride, until the chips are deeply saturated, and then by spraying onto the same chips a solution of a soluble silicate derivative, preferably potassium silicate, which reacts with the calcium salt to form calcium silicate in situ. This so formed calcium silicate stabilizes the wood fibers by immobilizing the same and thus transforms the wood chips into aggregates that are chemically inert, dimensionally stable, resistant to shivering and long lasting under any kind of climatic conditions, thereby making them useful in the construction field.
In the same Canadian patent, it is disclosed that the so prepared wood aggregates can be used as a "filler" into any kind of mixtures used in the construction field, such as concretes, mortars and the like.
If the concrete mix produced with such stabilized wood aggregates have proved so far to be very useful, especially for insulation purposes, nobody has ever thought of using them for the manufacture of tiles, pavers or other "landscaping" blocks or components capable of withstanding pedestrian traffic, because, so far, all the blocks that were prepared from such a concrete mix and extensively tested have not proved to possess enough bending strength and enough abrasive resistance.
Moreover, for such a very specific application, it is compulsory that the tiles, pavers or blocks have a high porosity to make the area covered by the same self-draining and sound-absorbing at the very same time.